In integrated circuit packaging, it is common practice to bond the connectors of the integrated circuit chip to a printed circuit pattern on a substrate material, such as a ceramic material. Connection to the printed circuit pattern is made by pins which pass through the substrate and are conductively connected to the pattern on one side of the substrate and project perpendicular to the plane of the substrate on its opposite side. As the number of devices per integrated circuit chip increases and as the number of connections necessarily increases, it is obvious that the number of external connections, e.g. input/output (I/O), pins on the substrate, must also increase. Insertion of the pins of the substrate into a socket on a printed circuit board is a problem because of the additional force required to insert a plurality of pins into friction-type female connectors. The use of excessive force can create problems inherent with bent pins, misaligned female connectors and/or pins, and the possibility of bending pins during insertion. In addition, the use of large electronic modules has given rise to the need for dense area array connector systems.
There has recently come into being a dense area array connector system which overcomes the above-mentioned problems and which is adapted for use with a wide range of module sizes. The system is employed in a broad spectrum of applications to interconnect modules and cards to mating printed circuit boards and it is fully disclosed in U.S. Pat. No. 3,915,537. Briefly, the system comprises a zero insertion force electrical connector which is adapted for incorporation into a printed circuit board or similar arrangement. The connector comprises a bifurcated spring yoke having flat longitudinally and upwardly extending arms, each with cylindrical or barrel-shaped contact surfaces in opposing and spaced apart relationship and chamfered at their respective entry ends to facilitate entry of the pin into the gap between said surfaces. The connector includes a longitudinally and downwardly extending mounting post or stem adapted to connect the connector device with a printed circuit board.
The elimination of insertion forces is accomplished by first locating the connecting pins in an area at a position adjacent the chamfered ends of the contact surfaces and then moving the pins slideably and transversely in guided relation between the opposing contact surfaces.
Alternately, the shaping of the contact surfaces and the resiliency of the upwardly extending arm provides an electrical connector having a low insertion force when the pin is longitudinally introduced between the contact surfaces, the opposing cylindrical or barrel-shaped surfaces serving the function of the chamfers during insertion of the pin. But in either the transverse or in-line-insertion, the opposing contact surfaces will assure line contact of each contact arm with the pin.
With the advent of larger pluggable modules having a higher count or number of I/O pins, it became desirable to employ the above-described dense area array connector system and to use the system in a zero insertion mode wherein the pins are slideably and transversely guided into engagement with the mating spring contact surface. It then became evident that what was needed was an actuating mechanism which would allow the module to be plugged in with the actuator serving as a camming vehicle as well as a module retention device. Examples of known actuating devices of this type are disclosed in IBM Technical Disclosure Bulletin, Vol. 16, No. 12, May 1974, pages 3975-3976; and, also in U.S. Pat. No. 4,059,323. These devices proved to be complex and expensive and lacking in features that were desired.